Antibody responses of the IgE isotype, like other immunoglobulin classes, are regulated by a finely-tuned network of complex positive and negative regulatory factors. This paper reviews studies concerning abnormalities of histamine-induced suppressor T cell activity in atopic subjects.
In atopic subjects, there is a reduction in the generation of histamine-induced suppressor cell activity which positively correlates with decreased phenotypic expression of histamine-type 2 receptors on T lymphocytes. Nonatopic control subjects with systemic mastocytosis have normal functional
and phenotypic data, suggesting that chronic in vivo activation by histamine of T cells from atopies does not explain the abnormal histamine-induced suppressor response. Proper functioning of the histamine-induced suppressor cell system involves obligatory interactions between lymphocytes
and monocytes. Monocytes from atopic subjects produced significantly less prostaglandin E2 in response to exogenous histamine-induced suppressor factor. A new immunostimulatory drug, Fanetizole mesylate, partially corrects the abnormal histamine-induced suppressor response. Clinical
application of this information may lead to new treatments of the atopic diathesis.

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